The invention relates to internal combustion engines and particular to such engines with energy recovery systems.
Superchargers are air pumps or blowers in the intake system of an internal combustion engine for increasing the mass flow rate of air charge and consequent power output from a given engine size. Turbosuperchargers (normally called turbochargers) are engine exhaust gas turbine driven superchargers. When superchargers are driven mechanically from the shaft of the internal combustion engine, a speed increasing gear box or belt drive is needed. Such superchargers are limited to a relatively low rotating speed and are large in size. Paxon Blowers and Vortech Engineering Co. are marketing such superchargers. Fixed gear ratio superchargers suffer from two very undesirable features: 1) there is a sharp decrease in boost pressure at low engine RPM because boost pressure goes generally to the square of the speed of rotation, and 2) it is generally difficult to disconnect the supercharger from the engine when the supercharger is not needed.
Applicant was granted on Dec. 5, 1995 a patent (U.S. Pat. No. 5,471,965) on a very high-speed radial inflow hydraulic turbine. FIG. 12 of that patent discloses the hydraulic turbine driven blower used in combination with a conventional turbocharger to supercharge an internal combustion engine. In that embodiment the output of the hydraulic driven compressor was input to the compressor of the conventional turbocharger. In all the embodiments shown in the ""965 patent, the pump delivering high-pressure hydraulic fluid to the hydraulic turbine was driven directly off the engine shaft. At high speeds when the exhaust driven turbosupercharger is fully capable of supplying sufficient compressed air to the engine, a bypass valve unloaded the hydraulic fluid pump. Other supercharger patents granted to me include U.S. Pat. Nos. 5,937,833, 5,937,832, 5,924,286, and 5,421,310 all of which along with the ""965 patent are incorporated herein by reference.
Another hybrid supercharger is disclosed in U.S. Pat. No. 4,285,200 issued to Byrne on Aug. 25, 1981. That patent disclosed a compressor driven by an exhaust driven turbine and a hydraulic driven turbine, the compressor and both turbines being on the same shaft. That turbine was an axial flow turbine and the turbine was driven with engine oil. With this design oil foaming can be a problem. U.S. Pat. No. 5,471,965 and U.S. Pat. No. 4,285,200 are incorporated herein by reference.
There is a great need for improving the efficiency and output power of internal combustion engines, especially diesel engines. In the low RPM range, the currently available turbocharging systems are not very effective in producing sufficient engine manifold pressure and power, required for satisfactory vehicle acceleration and exhaust smoke reduction. This applies especially to xe2x80x9cstop and goxe2x80x9d type services, such as city buses and trash collecting trucks. It is typical to utilize the energy in engine exhaust gas to supercharge diesel engines; however at high engine speeds the exhaust gas energy is greatly in excess of that which is needed for supercharging and the excess energy is wasted.
What is needed, is an efficient system to put this wasted energy to use.
The present invention provides an exhaust power recovery system for internal combustion engines. The engine exhaust gases drive a gas turbine that in turn drives a hydraulic turbine pump pressurizing a hydraulic fluid which then in turn is the driving source for a hydraulic motor which transmits power to the engine shaft. In a preferred embodiment for a turbocharged engine, the hydraulic fluid is also used as the drive fluid in a hydraulic supercharger system that provides additional supercharging at low engine speeds to supplement the exhaust driven turbocharging system. In this embodiment the pressurized hydraulic fluid for driving the supercharger hydraulic turbine is provided by a pump driven by the engine shaft. A hydraulic fluid control system is provided to match compressed air flow with engine needs. In this preferred embodiment more than enough energy is recovered from the exhaust gasses by the exhaust power recovery system to operate the hydraulic supercharger system. The horsepower of a 280 horsepower turbocharged diesel engine is increased by about 20 percent to about 335 horsepower. As to fuel efficiency, Applicant estimates that a cross country diesel truck operating 12 hours per day, 300 days per year will save between 6,000 and 10,000 pounds of fuel per year with substantial reductions in emitted pollutants.